Philippine marines say they have seized thousands of blasting caps and a detonator from a ferry on the southern island of Jolo.

Authorities say 6,000 blasting caps were discovered Thursday on board the boat. A passenger was also taken into custody after police found explosives in his bag. The man had earlier refused to allow authorities to inspect his belongings.

Officials say passengers were ordered off the ferry immediately following the discovery.

The ferry was headed to Siasi island from Jolo, which is a stronghold of the militant group Abu Sayyaf. The group has been blamed for a series of attacks in the southern Philippines.